Altitude sickness natural history, complications and prognosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Natural History
Complications
The most serious symptoms of altitude sickness are due to edema (fluid accumulation in the tissues of the body). At very high altitude, humans can get either high altitude pulmonary edema (HAPE), or high altitude cerebral edema (HACE). The physiological cause of altitude-induced edema is not conclusively established. It is currently believed, however, that HACE is caused by local vasodilation of cerebral blood vessels in response to hypoxia, resulting in greater blood flow and, consequently, greater capillary pressures. On the other hand, HAPE may be due to general vasoconstriction in the pulmonary circulation (normally a response to regional ventilation-perfusion mismatches) which, with constant or increased cardiac output, also leads to increases in capillary pressures. For those suffering HACE, dexamethasone may provide temporary relief from symptoms in order to keep descending under their own power.
HAPE occurs in ~2% of those who are adjusting to altitudes of ~3000 m (10,000 feet) or more. It can progress rapidly and is often fatal. Symptoms include:
- Fatigue
- Severe dyspnea at rest
- Cough that is initially dry but may progress to produce pink, frothy sputum.
Descent to lower altitudes alleviates the symptoms of HAPE.
HACE is a life threatening condition that can lead to coma or death. It generally occurs after a week or more at high altitude, but symptoms of mild HACE can sometimes show up even after a few hours at higher altitudes. It occurs in about 1% of people adjusting to altitudes above ~2700 m (9,000 feet). Symptoms include:
- Bladder dysfunction
- Bowel dysfunction
- Coma
- Confusion
- Fatigue
- Hallucinations
- Headache
- Irrational behavior
- Loss of coordination
- Loss of memory
- paralysis on one side of the body
- Visual impairment
Descent to lower altitudes may save those afflicted with HACE.
Prognosis
Most cases are mild, and symptoms improve promptly with a return to lower altitude. Severe cases may result in death due to respiratory distress or brain swelling (cerebral edema). In remote locations, emergency evacuation may not be possible, or treatment may be delayed. These conditions could adversely affect the outcome.